This study will form a basis for an investigation of the biomechanical responses of the lumbar spine to chiropractic manual palpation. A method will be provided for obtaining force-displacement data during a chiropractic assessment of vertebral motion. A force transducer will be designed and tested to measure the directed forces during a manual assessment of motion in the lumbar spine. The limits of its use during manual assessment will be determined by repeatability and reliability testing of the device on volunteer subjects using two trained chiro- practic examiners. After a training period to establish rating uniformity, the examiners will assess the lumbar spine for restrictions in motion in each of the 3 planes of motion (ie; lateral bending, axial rotation and extension). The rating scale will be a 5 point scale with 0 signifying no restriction to 4 signifying high restriction. The manual assessment and force will be simultaneously measured. The feasibility of obtaining force-displacement data by measuring both intervertebral 3-D kinematics and the directed forces necessary to induce passive motion will then be tested. Intervertebral kinematics and applied forces will be measured simultaneous to the performance of a chiropractic manual palpation. 3-D motion will be measured using a pair of infra-red light sensitive, opto-electronic motion sensing cameras (WATSMART, Northern Digital, Waterloo, Ontario). Rigid clusters of infra-red-light emitting diodes will be attached to each of four lumbar vertebra via 2.0 mm stainless steel pins inserted into the spinous processes. This system will measure vertebral motion with 6 degrees of freedom (3 rotations and 3 translations) with an accuracy of 0.5 degrees rotation and 0.5 mm translation.